Question

1. in late 1995, a gallup survey reported that americans approved of sending troops to bosnia by 40% to 46% approval rate. the poll did not mention that 20,000 u.s. troops were committed to go. a cbs news poll mentioned the 20,000 figure and got the opposite outcome—a 33% to 58% disapproval rate. briefly explain why the mention of the number of troops would cause such a big difference in the poll results. write the name for the kind of bias that is at work here.
2. a church group interested in promoting volunteerism in a community chooses an srs of 200 community addresses and sends members to visit these addresses during weekday working hours to inquire about the residents’ attitudes toward volunteer work. sixty percent of all respondents say that they would be willing to donate at least an hour a week to some volunteer organization. bias is present in this sample design. identify the type of bias involved and state whether you think the sample percent obtained is higher or lower than the true population percent.
3. to gather data on a 1200 - acre pine forest in louisiana, the u.s. forest service laid a grid of 1410 equally spaced circular plots over a map of the forest. a ground survey visited a sample of 10% of these plots. (a) how would you label the plots? (b) use the table of random digits beginning at line 105 (below) to choose the first 2 plots in an srs of 141 plots. 95592 94007 69971 91481 60779 53791 17297 59335 68417 35013 15529 72765 85089 57067 50211 47487

Explanation:

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The mention of 20,000 troops provides new and potentially concerning information to respondents. This can change their perception and decision - making in the poll. The bias at work is response bias, specifically information bias. The new information about the large number of troops influences the responses.

The sample is chosen to visit during weekday working hours. This means that people who are at work during these hours (a large segment of the population) are less likely to be included in the sample. This is non - response bias. Since those who are more likely to be at home (e.g., retirees, stay - at - home parents) are more likely to respond, and they may be more likely to be willing to volunteer, the sample percent is likely higher than the true population percent.

(a) We can label the 1410 plots from 0001 to 1410. This four - digit labeling system allows us to use random digit tables easily.
(b) We read the random digits in groups of 4. Ignore numbers outside the range 0001 - 1410 and repeated numbers. Starting at line 105:

Step1: Read the first four - digit number 9559. It is outside the range 0001 - 1410, so we ignore it.

Step2: Read the next four - digit number 9400. It is outside the range 0001 - 1410, so we ignore it.

Step3: Read the next four - digit number 7699. It is outside the range 0001 - 1410, so we ignore it.

Step4: Read the next four - digit number 7191. It is outside the range 0001 - 1410, so we ignore it.

Step5: Read the next four - digit number 4816. It is outside the range 0001 - 1410, so we ignore it.

Step6: Read the next four - digit number 0779. It is within the range 0001 - 1410, so the first plot is plot 0779.

Step7: Continue reading. The next four - digit number 5379. It is outside the range 0001 - 1410, so we ignore it.

Step8: Read the next four - digit number 1172. It is within the range 0001 - 1410, so the second plot is plot 1172.

Answer:

The mention of the number of troops causes a big difference because it provides new information that affects respondents' attitudes. The bias is information bias.

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